Taste distinguishes water-soluble salt, sugar, acid, and base chemicals {taste, physiology}. Taste receptors are for only salt, sugar, acid, or base. For example, salt taste receptors measure salt concentration as salt-to-receptor binding per second. Different taste receptors converge on taste neurons. Similar taste sensations vary only in intensity, not in quality, because similar receptors go to same taste neuron.
Salty chemicals are small and ionic and have neutral acidity. Sodium-chloride sodium ions make pure salt taste. Potassium-chloride potassium ions make salt and bitter taste.
Sour chemicals are small, ionic, and acidic. Hydrogen chloride makes pure sour taste.
Sweet chemicals are large and polar and have neutral acidity. Glucose makes pure sweet taste. Fructose and galactose are sweet.
Bitter chemicals are small or large, ionic, and basic. Hydroxide ions make pure bitter taste.
Savory chemicals are large, ionic-polar, and slightly acidic. L-glutamic acid sodium salt (monosodium glutamate) tastes distinctively salty and sweet.
Taste neurons inhibit and excite each other to compare sugar, acid, base, salt, and L-glutamate receptor inputs to find differences and indicate taste types [Kadohisa et al., 2005] [Pritchard and Norgren, 2004] [Rolls and Scott, 2003].
Tastes are relative. For example, salt only tastes salty relative to other tastes [Brillat-Savarin, 1825]. Saliva salt level is highest in morning, drops until afternoon, and then rises again to high morning value, so salt amount needed for salt taste varies during day. Saliva substance concentrations can vary tenfold. Tongue taste-receptor pattern affects taste.
Taste is painful at high concentrations. Taste can detect low concentrations.
Taste can detect source location. Taste can detect several sources from one location.
acidity
Molecule atoms, bonds, and electric charge determine acidity, which can be acidic, neutral, or basic.
Sour is acidic. Salty is neutral acidity. Savory is neutral. Sweet is neutral. Bitter is basic.
Salty, savory, and sweet have similar neutrality.
Sour and bitter have opposite acidity.
ionicity
Molecule atoms and bonds and molecule-electron properties determine ionicity, which can be ionic or polar.
Sweet and some bitters are polar. Salty, savory, sour, and some bitters are ionic.
Sour and sweet, salty and sweet, and savory and sweet have opposite ionicity.
size
Sour and some bitters have similar small size.
Salts have medium size.
Sweet, savory, and some bitters have similar large size.
polarity or ionicity; acidity, neutrality, or basicity; and size
Taste molecules have a combination of polarity or ionicity; acidity, neutrality, or basicity; and size.
Taste molecules can be:
acidic: hydrogen ion (sour)
neutral: monosodium glutamate (savory)
neutral: sodium chloride and potassium chloride (salt)
neutral: glucose and fructose (sweet)
slightly basic: phenylthiourea, phenylthiocarbamide, and 6-n-propylthiouracil (bitter)
basic: hydroxide ion (bitter)
Taste molecules can be:
polar: glucose and fructose (sweet)
polar: phenylthiourea, phenylthiocarbamide, and 6-n-propylthiouracil (bitter)
ionic: hydroxide ion (bitter)
ionic: hydrogen ion (sour)
ionic: sodium chloride and potassium chloride (salt)
ionic: monosodium glutamate (savory)
(They cannot be non-polar, because non-polar does not dissolve in water.)
Taste molecules can have molecular weight 1 to 200:
1: hydrogen ion (sour)
17: hydroxide ion (bitter)
58: sodium chloride (salt)
75: potassium chloride (salt)
152: phenylthiourea and phenylthiocarbamide (bitter)
169: monosodium glutamate (savory)
170: 6-n-propylthiouracil (bitter)
180: glucose and fructose (sweet)
Taste molecules are:
Sour: acidic, ionic, and small.
Salt: neutral, ionic, and medium.
Savory: neutral, ionic, and large.
Sweet: neutral, polar, and large.
Bitter: slightly basic, polar, and large.
Bitter: basic, ionic, and small.
Acidic and polar do not exist, because acids are ionic. Basic and polar do not exist, because bases are ionic.
Small and polar do not exist, because small molecules are ionic. Medium and polar do not exist, because medium molecules are ionic.
Small and neutral do not exist, because small molecules have hydrogen ions or hydroxide ions. Large and acidic do not exist, because acidic molecules have small hydrogen ions. Large and basic do not exist, because basic molecules have small hydroxide ions.
Taste molecules fall into six categories:
Large polar: neutral (sweet) or slightly basic (bitter)
Large ionic: neutral (savory)
Medium ionic: neutral (salt)
Small ionic: acidic (sour) or basic (bitter).
If new flavor associates with gastrointestinal illness, people are averse to the flavor {learned taste aversion}.
Taste receptors adjust for current saliva substance concentrations. Taste stimulus at same concentration as saliva concentration is tasteless {taste zero}.
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Date Modified: 2022.0225